The present disclosure relates generally to collars for power transmission, and more particularly to an improved collar system for attaching components to a rotating drive shaft.
A basic component in the power transmission industry is the shaft collar. The importance of shaft collars is demonstrated through their widespread use in the industry. Shaft collars are used for various applications including mechanical stops, locating components and bearing spacers. Shaft collars are frequently accessories to other components to create assemblies for many types of power transmission equipment including motors and gearboxes. Shaft collars and couplings are used to attach components such as gears, sprockets and pulleys to shafts in applications when high amounts of torque are transmitted. As a result of such wide spread use, shaft collars have become well understood in the art.
Traditional shaft collars have utilized perpendicular set screws to generate coupling force, as the screw is tightened onto the shaft. The amount of coupling force applied by the screw varied according to the material and condition of the shaft to which the collar was connected. Preferably, in the past, the shaft had been made of a softer material than that of the set screw to allow the set screw point to impinge into the shaft. The impingement maintained the set screw and collar in position under torque and axial loads. However, the impingement of the set screw damaged the shaft by creating an eruption of material around the set screw point, i.e. a raised burr on the surface of the shaft. This raised burr made it difficult to remove the collar from the shaft for replacement. Further, small angular or lateral adjustments were difficult if not impossible since the set screw point tends to seat back to the center of the original impingement.
In view of the above, several systems have been developed to improve set screw shaft collars. For example, some prior shaft collars had keyways for better holding power and more precise alignment. These keyways prevented rotational slippage on the shaft and created a positive drive for better torque transmission. Shaft collars with keyways were frequently used as components in handles, levers and the like. In linear applications, shaft collars often served as mechanical stops and spacers on keyed shafts. Shaft collars with keyways also increased stiffness and improved the alignment of thin keyed shaft elements such as pulleys and the like. Further, shaft collars with keyways held a fixed location on the shaft to allow for interchanging components thereon.
An alternative to set screw collars was clamp style shaft collars. Clamp style collars solved some of the problems that existed with the traditional set screw collars. Clamp style collars utilized screws to create the compressive forces that close the collar onto the shaft, thereby locking the clamp collar in position. When using clamp style shaft collars, the shaft was not damaged because set screws were not used. Clamp collars can be removed and adjusted. In addition, the holding performance of the clamp collars was improved over set screw collars because the holding power of the clamp collar did not depend on the impingement of the screw. Thus, shaft material was a relatively minor factor in how well a clamp collar performed. When the clamp collar screws were tightened, the screws closed the collar onto the shaft, creating a uniform distribution of forces around the circumference of the shaft.
One-piece clamp collars included a split ring with a threaded hole to receive a single screw. One-piece clamp collars used a portion of the force generated by the screw to compress the collar around the shaft. While set screw collars and one-piece clamp collars must slide over the end of a shaft, two-piece clamp collars can be disassembled and installed in position without having to remove other components from the shaft. Two-piece collars more efficiently use force than a one-piece clamp collar designs because they used the full force generated by the screws to apply clamping forces to the shaft.
Although clamp type collars worked very well under relatively constant loads, shock loads were known to cause the collar to shift position on the shaft. Further, in some applications, undesirable backlash was present. For applications with the above type problems, an undercut on the shaft was made. A two-piece clamp collar can be adapted and configured to mate with the undercut portion to create a positive stop that was more resistant to shock loads. In the case of an undercut shaft, a one-piece collar would have to be pried open to fit initially over the shaft and a set screw collar could not be installed properly in any case. As a result, only a two-piece collar clamp would be used in such circumstances. Additional techniques for preventing shifting and backlash included incorporating multiple spiral cuts to accommodate angular misalignment, parallel misalignment and axial motion.
When used as bearing spacers, it is important to achieve a close fit between the bearings and the clamp. If a clamp distorts and damages the shaft appreciably, the precision required for proper bearing performance is detrimentally affected. Therefore, the bearings need to be spaced an undesirable distance from the clamp in order to allow for the distortion caused thereby.
There are still further problems associated with coupling a hollow shaft onto a rotating shaft. Although set screw clamps may be the least costly, the inefficient holding force and damage to the shafts which resulted from the coupling have limited their application. Known clamping collars require serrations in the hollow shaft to allow for deformation. When the clamping force deforms the hollow shaft, the inner shaft is engaged. As a result, the hollow shaft is weakened and fine position adjustments become difficult because of the erratic deformations and common shaft damage.
In view of the above deficiencies, there is a need for improved clamp collars which permits easy installation, secures the shaft without damaging the shaft, aids in assuring adequate coupling without undesirable backlash and is easy to manufacture.
In one representative embodiment, the present disclosure provides a clamp for affixing a hollow shaft to a drive shaft. In such embodiment, the hollow shaft surrounds the drive shaft and defines opposing slots. In one representative embodiment, the clamp includes a first portion and a second portion. The first portion comprises a bridge with an outer surface and an inner surface. The inner surface of the bridge is adapted and configured to engage the drive shaft. The first portion also comprises two opposing arms, depending from the bridge. Each arm includes an inner contact face and a shoulder defining a hole for receiving a fastener. The second portion comprises an arch having an outer surface and an inner surface. The inner surface of the second portion is adapted and configured to engage the drive shaft. The second portion also includes two opposing members, upstanding from the arch portion. Each opposing member defines a bore to engage the fasteners. To assemble the first portion and the second portion about the slotted portion of the hollow shaft, the fasteners are deployed to engage the bores through the holes. As the fasteners are tightened, the first portion and the second portion are drawn together such that each inner surface couples to the hollow shaft and the first portion compresses thereby affixing the inner contact faces to the drive shaft.
In another representative embodiment, a clamp for coupling a slotted tube to a shaft is disclosed. The clamp comprises a lower portion defining a timing slot profiled to receive the slotted tube. The lower portion also defines two threaded throughbores to receive fasteners. The clamp also includes an upper portion having a depending face profiled to receive the slotted tube in a close fitting relationship. The depending face opposes the timing slot. The upper portion also includes two opposing arms for engaging the shaft and two voids intermediate the two arms and the depending face. The voids allow the two arms to flex. Further, the upper portion includes two shoulders defining throughbores. Each shoulder extends from the arms such that when the fasteners are deployed in the throughbores to couple the two threaded throughbores, the timing slot and the depending face are urged together to engage the tube and the two arms are urged together to engage the shaft.
In still another representative embodiment, a device for affixing a tube around a shaft is provided. The device comprises a first element including a middle portion for engaging the shaft. The first element also includes a first arm and a second arm depending from the middle portion in a flexible manner and a first flange integral with and inclined at an angle to the first arm. A second flange is integral with and inclined at an angle to the second arm. Both the first flange and the second flange have a hole. A second element includes a central portion which opposes the middle portion. The central portion engages the shaft. A first end, upstanding from the central portion, defines a first bore in alignment with the first hole and a second end, upstanding from the central portion, defines a second bore in alignment with the second hole, whereby, deploying a first fastener in the first hole and the first bore and employing a second fastener in the second hole and the second bore brings the first arm and the second arm closer together to engage the shaft as well as bringing the middle portion and the central portion closer together to engage the tube thereby affixing the tube to the shaft.
In another representative embodiment, a device operatively connects a tube to a shaft. The tube surrounds the shaft and the device includes a first member and a second member. The first member includes a bridge and at least two opposing arms operatively connected to the bridge. Each arm includes a shoulder, where each shoulder has a hole operatively positioned therein. The second member includes a center portion for engaging the tube and at least two opposing members. Each opposing member has a bore operatively positioned therein for engaging a fastener such that upon operatively positioning the first member and the second member relative to the tube and drawing the first member and the second member together, the tube is operatively connected to the shaft.
These and other unique features of the system disclosed herein will become more readily apparent from the following description, the accompanying drawings and the appended claims.